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Experience against urban flooding in Japan and China

Hong Kong has successfully applied anti-flooding underground tanks, while some places have developed a “sponge city” model.

The historic rain on May 29 caused Severe flooding in HanoiMinister of Natural Resources and Environment Tran Hong Ha said that the capital could consider building an underground water tank in an area that is often locally flooded.

In fact, the idea of ​​an underground water tank has been around for a long time, and has been successfully applied in many places around the world such as Hong Kong (China). According to Prof. Dr. Tran Duc Ha, Director of the Institute of Water Supply and Sewerage, underground water tanks are often applied to locally flooded areas, the trend is stable over the years.

To deploy, the water supply and drainage agency identifies the flooded area, finds a location with a convenient water path, and a large empty space above to build an underground tank. The ideal area is under large lawns, football fields to optimize tank volume, to help water seep quickly.





Describe the operation of an underground anti-flood water tank in Hong Kong (China).  Photo: Iwa-network.org

Describe the operation of an underground anti-flood water tank in Hong Kong (China). Image: Iwa-network.org

When it rains heavily, the amount of water will flow quickly into the tank, reducing pressure on the drainage system, avoiding flooding. “The amount of water stored can be used for irrigation in the dry season, for fire fighting or brought back to the plant to be treated as domestic water,” Ha said.

In Hong Kong, in the large underground tanks, there are works located under the Happy Valley amusement park. The tank has a volume of about 60,000 m3, L-shaped and located under 5 football fields, which has effectively supported flood prevention over the years.

Regarding this model, Mr. Ha thinks that it is necessary to separate the underground water storage tank and the underground drainage system. The underground tunnel system has a much larger scale and cost.

Drainage tunnels are connected to treatment plants, or lead directly to rivers and lakes. The advantage is that rainwater and wastewater are collected in separate pipes, helping to limit the risk of flooding and water pollution.

When rainwater flows into the underground system, it will follow pipes to rivers and lakes… And wastewater will be treated by separate pipes, in a closed process and only discharged into the environment after it has been treated. done deal.

One of the most advanced underground drainage systems in the world is in Tokyo. In this system, the MAOUDC is the world’s largest flood protection structure, which is said to be an underground shield that protects the Japanese capital from flooding.





Employees at the MAOUDC flood control system in Kasukabe, north of Tokyo, September 3, 2020.  Photo: AFP

Employees at the MAOUDC flood control system in Kasukabe, north of Tokyo, September 3, 2020. Image: AFP

This system of underground tunnels sucks water from small and medium rivers in the northern Tokyo area, pouring it into 5 giant underground tanks, each 70 m high. The water in the underground tank will then be circulated through a 6.3 km long tunnel and discharged by 78 large capacity pumps into the Edo River at a speed of nearly 200 m3/s.

If the water in the Edo River rises, MAOUDC will reduce the flow through a giant pressure control tank the size of two football fields, so that the pumps can regulate and push the water into the river.

Presenting the idea of ​​a flood-proof model for Hanoi, Prof. Dr. Nguyen Van Lien, former Deputy Minister of Construction, said that the most important thing is to create a drainage space, apply materials with high permeability and expand the area. water surface, grass surface.

In the world, the method Mr. Lien mentioned is called “sponge city”. This is a term for urban areas to deal with flooding by natural means, instead of forcing water out by pipes and pumps.

The main measures used are emptying many trees on the rooftops of high-rise buildings, designing many tanks to store rain water, building pavements using porous materials, planting trees with the function of absorbing and keeping water in urban; expanding lakes, lagoons, spaces to store water…





Describe the anti-flooding of the city of sponges.  Photo: CBBC Focus

Describe how to prevent flooding of the “sponge city”. Image: CBBC Focus

CBBC Focus showed that a city just need to change road construction materials with water-absorbent materials, increase planting of trees on the rooftops of high-rise buildings, can significantly reduce small and medium floods.

According to Kongjian Yu, Dean of the Department of Architecture and Landscape Architecture of Peking University, the “sponge city” is a city that can keep, clean and drain water in a natural way, this is the approach Ecological.

Therefore, instead of draining it all, this model retains rainwater for urban agriculture, re-charges it into underground water sources for the long-term, or treats it to bring it to people’s daily life. Currently, Wuhan, Beijing and Shanghai are leading cities in the development of “sponge cities”.

Son Ha

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